Initial highlights of the HOBYS key program, the<i>Herschel</i>imaging survey of OB young stellar objects

We present the initial highlights of the HOBYS key program, which are based on <i>Herschel<i/> images of the Rosette molecular complex and maps of the RCW120 H ii region. Using both SPIRE at 250/350/500 <i>μ<i/>m and PACS at 70/160 <i>μ<i/>m or 100/160 <i>μ<i/>m, the HOBYS survey provides an unbiased and complete census of intermediate- to high-mass young stellar objects, some of which are not detected by <i>Spitzer<i/>. Key core properties, such as bolometric luminosity and mass (as derived from spectral energy distributions), are used to constrain their evolutionary stages. We identify a handful of high-mass prestellar cores and show that their lifetimes could be shorter in the Rosette molecular complex than in nearby low-mass star-forming regions. We also quantify the impact of expanding H ii regions on the star formation process acting in both Rosette and RCW 120.